Cosmology is the study that handles all the really big questions about the universe, many of them are questions that have been perplexing philosophers for years. Questions like when it all began? And whether or not the universe has always expanded like it is doing now? Those questions have actually been answered, but one they have yet to answer is when and how is the universe going to end?
Believe it or not, that answer may be closer than you might think. In the past 20 years or so, the astrophysicists of the world have been learning that our universe is actually driving itself apart. Scientists have long known that other galaxies are all moving away our galaxy, and the one that are farthest away are the ones that are moving faster than the others. The only explanation for this is that the universe is presently expanding. Logic and the laws of gravity would tell us that this expansion should be slowing down. But this is not what’s actually happening – the universe is now expanding at a faster rate!
Since no one really knows what is responsible for this acceleration, cosmologists attributed it to something else that know little about – and that is dark energy. Much of the activity in space today is believed to be the influence of dark energy. As far as discussion about the end of the universe, dark energy is helped create many interesting theories.
The Big Rip
No one really knows what dark energy really is, therefore no one knows what it is going to do in the future either. In year 2003, Robert Caldwell from Dartmouth College came up with a new theory about the expanding universe. He proposed that the acceleration rate would increase with time.
If we imagine a car driver who floors the gas pedal without having limited acceleration. As his car speeds up and it goes faster — the velocity change would greatly increase over time — and the car would eventually fly apart and break into hundreds of pieces as the forces of friction took over.
A similar kind of thing would occur within a universe that experiencing relentless acceleration. We would see galaxies being destroyed, and the solar system would unwind and the planets would eventually explode as the rapid space expansion would rip atoms apart.
Present theories are predicting that if the Big Rip is going to occur, it is going to take another 22 billion years to take place.
The Big Freeze
There are several theories out there right now that are suggesting that dark energy is a cosmological constant – a type of energy that is uniform and is present throughout the universe. “If the cosmological constant is the dominant thing in the universe,” says Mark Trodden, who is presently a co-director from the Penn Center for Particle Cosmology located at the University of Pennsylvania, then rather than speeding up and eventually ripping itself apart, the universe would simply continue to expand — forever and ever. “If the cosmological constant continues to dominate, the universe will continue to accelerate and that’s it.”
This may sound harmless, but it’s not. As this dark energy keeps driving the acceleration in our expanding universe, the light from distant galaxies will not be visible as they would way too far away. This would cause entropy to keep increasing as well. The formation of stars will cease in about 100 trillion years or so because all the matter that fuels them will be exhausted. All the black holes will evaporate, and matter will then decay into radiation. The universe will be left as a very cold lifeless place for all of eternity. This very dark future is called the Big Freeze.
The False Vacuum
There is also the chance that this elusive dark energy will matter in the end. Other scenarios that have been considered have are assuming that our universe is accounted for. But maybe there is more out there, and perhaps our universe is just a small portion of a much larger multiverse? Is it possible that other universes will affect the fate of our universe?
Many experts are saying yes. “Imagine you go to a very, very large scale — much larger than our current observable universe,” points out Jonathan Braden, who is a cosmologist from University College London. While our universe is quite homogenous and pretty constant everywhere, a much larger view of it could reveal that it is only a little pocket that has its own set of physical laws and parameters, which are quite different from the bigger multiverse.
If this is the case, it could mean that our universe is in a strange state that is called a false vacuum. This is when we wrongly assume that we are in a stable state, but it is actually still possible to drop to another state very quickly. Braden says this would cause a phase transition, which is very similar to how water would change from a liquid to a gas at its boiling point — only this would happen to the entire universe. Generally speaking, our cosmos would behave like bubbles boiling in a pan of water, he claims, because of the change to the universe’s laws and constants. “Eventually these bubbles can run into each other, and from our viewpoint it would be like our universe … collided with another universe.”